Effects of water current on swimming performance, ventilation frequency, and feeding behavior of young seahorses (Hippocampus erectus)

Seahorses are poor swimmers, and their dispersion is a topic of increasing interest for their conservation. In the present study, the swimming performance, ventilation, and feeding behavior of the young seahorses Hippocampus erectus Perry, 1810 under simulated water currents (control-, low-, mid-, and high velocities) were investigated. Between 25.0% and 33.9% of the seahorses in the experimental groups (3, 10, and 30 days post birth [DPB]) stayed attaching to the substrate, and the rest swam if there was no water current; however, the attachment rates of the 10 and 30 DPB seahorses increased significantly in the high velocity treatment (P < 0.05). The ventilation rates decreased significantly with the increase of seahorse age under the high water current, regardless of whether they were swimming or attaching (P < 0.05). For all of the groups, the high water current could significantly decrease the total feeding frequency (TFF) and effective feeding frequency (EFF), with the swimming seahorses having a higher feeding frequency than that of the attaching seahorses. The young seahorses in the high water current treatment had lower growth rates and suffered total mortality by the end of 30 day experiment.